The present invention is related generally to primary electrochemical cells and is more particularly concerned with a novel primary electrochemical cell which is hermetically sealed and a method for its production.
Primary electrochemical cells have been known for some time and have been utilized in a wide variety of applications. Certain of these applications require that the cell be hermetically sealed in order to preclude the possibility of any of the contents escaping into the surrounding environment. Two such applications are where the cell is used in a vacuum such as in space installations and where the cell is used in a device which is implanted within the human body, such as a heart pacer. In both of these classes of applications, reliability of the primary electrochemical cells is extremely important. This reliability includes protection against leakage of the contained electrolytic solution.
Previously, the technique which has been utilized to form a hermetically sealed primary electriochemical cell has involved the emplacement of a tubular feedthrough in either a wall of the cell container or in a glass-to-metal seal utilized at the closure of the cell container. This technique has a number of significant disadvantages. Firstly, the simple mechanics of filling the primary electrochemical cell with the electrolytic solution through a small opening such as is present in such a feedthrough device requires the initial evacuation of the container followed by backfilling with the electrolytic solution. This is time consuming and each container must be weighed individually in order to determine if the proper amount of electrolytic solution has been added. Furthermore, contamination of the feedthrough tubing during the filling process necessarily takes place and makes it difficult and often impossible to achieve a hermetic seal in that tubing to finally close off the container.